1. Field of the Invention
The present invention relates to a simultaneous discharge device for etching or ashing a coat formed on the surface of a material to be treated such as a semiconductor wafer or the like through discharging inside two chambers simultaneously with one high-frequency power supply.
2. Description of the Relevant Art
There is already known a simultaneous discharge device for discharging inside two chambers simultaneously with one high-frequency power supply which connects first respective ends of two Rf cables 101 to output terminals of a high-frequency power supply 100 and connects the other ends thereof to first plate-like electrodes 104, 105 in two chambers 102, 103 ,as shown in FIG. 5. Then, second plate-like electrodes 106, 107 are connected to ground.
According to the known device, although a single discharge does not make a wide difference in the rate of etching or ashing, simultaneous discharging inside of the two chambers by one high-frequency power supply does make a wide difference because there is some difference in impedance between the chambers 102 and 103 and the current tends to flow toward the chamber having the lower impedance. This is a problem.
This difference in impedance is caused by inherent differences in the arrangement of the first plate-like electrodes 104 and 105, the second plate-like electrodes 106 and 107, the Rf cables 101 and so on.